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Dmitry [639]
3 years ago
9

A sample initially contains 8.0 moles of a radioactive isotope. How much of the sample remains after four half-lives? Express yo

ur answer using two significant figures.
Chemistry
1 answer:
Tju [1.3M]3 years ago
6 0

Answer:

0.50 mol

Explanation:

The half-life is <em>the time required for the amount of a radioactive isotope to decay to half that amount</em>.

Initially, there are 8.0 moles.

  • After 1 half-life, there remain 1/2 × 8.0 mol = 4.0 mol.
  • After 2 half-lives, there remain 1/2 × 4.0 mol = 2.0 mol.
  • After 3 half-lives, there remain 1/2 × 2.0 mol = 1.0 mol.
  • After 4 half-lives, there remain 1/2 × 1.0 mol = 0.50 mol.

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Which best describes how magnesium (Mg) and oxygen (O) bond?
Ksivusya [100]

Answer:

a

They form an ionic bond by exchanging two electrons.

Explanation:

Magnesium loses two electrons and oxygen gains these electrons so ionic bond is formed

8 0
3 years ago
what is molarity of a sodium hydroxide solution made by combining 2.0 L of 0.60 M NaOH with 495 mL of 3.0 M NaOH? Assume the vol
hammer [34]

Answer:

Molarity of the sodium hydroxide solution is 1.443 M/L

Explanation:

Given;

0.60 M concentration of NaOH contains 2.0 L

3.0 M concentration of NaOH contains 495 mL

Molarity is given as concentration of the solute per liters of the solvent.

If the volumes of the two solutions are additive, then;

the total volume of NaOH = 2 L + 0.495 L = 2.495 L

the total concentration of NaOH = 0.6 M + 3.0 M = 3.6 M

Molarity of NaOH solution = 3.6 / 2.495

Molarity of NaOH solution = 1.443 M/L

Therefore, molarity of the sodium hydroxide solution is 1.443 M/L

8 0
3 years ago
Why must power plants spend so much money and be so cautious in dealing with these materials?
shepuryov [24]
If you are referring to nuclear power plants and radioactive materials, then there is a high necessity to be cautious and stay safe because only by being safe you can prevent accidents like those caused in Ukraine and Japan. Unlike other types of power plants whose destruction in case of an accident can relatively easily be contained, nuclear power plants are extremely difficult to manage if things go out of hand since you can destroy the air around it, the water, the food by ruining the soil, and many other things.
8 0
3 years ago
In your own words, please describe the difference between a complete ionic equation and a net ionic equation.
beks73 [17]

Explanation:

In the molecular equation for a reaction, all of the reactants and products are represented as neutral molecules (even soluble ionic compounds and strong acids). In the complete ionic equation, soluble ionic compounds and strong acids are rewritten as dissociated ions.

The net ionic equation is a chemical equation for a reaction that lists only those species participating in the reaction. The net ionic equation is commonly used in acid-base neutralization reactions, double displacement reactions, and redox reactions.

6 0
3 years ago
(Q014) Silicates a. are classified on the basis of what kind of metals they contain. b. form through the evaporation of water. c
Leni [432]

Answer: d. have the silicon-oxygen tetrahedron as their structural unit.

Explanation:

Silicates are anions that have both Oxygen and Silicon as the basis of their structure. These two form a tetrahedron type structure that enable them to be useful for a whole lot of things.

Silicates are very abundant on Earth as they comprise around 95% of the Earth's crust as well as the upper mantle which explains why they are mostly found in igneous rocks.

3 0
3 years ago
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